Typically, portable electronic apparatuses, such as portable terminals, MP3 players, Portable Multimedia Players (PMPs), and the like, allow users to enjoy various contents while carrying them. Such portable electronic apparatuses are becoming multifunctional and miniaturized according to consumers' demands. The portable electronic apparatus includes an input device for allowing a user to select and input a desired function and to see the selected function on a liquid crystal screen. The input device includes input components of various types such as a key-button type, a touch-key type, or a Navigation (hereinafter, “Navi” for short)-key type.
Generally, a key input scheme such as a Navi key or a touch key is used as a key indicating menu or additional-function selection, and a button key or a touch key is used as a key indicating a number or a character.
In particular, for a portable terminal, 3×4 numeric keys and functional keys indicating various functions such as “send”, “cancel”, “menu”, or “search” use touch keys in general.
FIG. 1 is an exploded perspective view of layers forming a conventional touch key 10, and FIGS. 2 and 3 are a perspective view and a plane view showing a combined state of the layers forming the conventional touch key 10, respectively.
As shown in FIGS. 1 to 3, the touch key 10 is formed outside a menu key or a Navi key formed in the center. The touch key 10 is formed by combining a plurality of layers such as a touch layer 12, including a first layer 12a and a second layer 12b where circuits are formed, and an upper layer 11 and a lower layer 13 formed on and under the first layer 12a and the second layer 12b, respectively.
The touch key 10 including the layers 11, 12, and 13 may be divided into a touch sensing unit 20 for sensing a touch, and a connector unit 30 extending from one end of the touch sensing unit 20 for electrically connecting to a printed circuit board (not shown) of a main body. A ground layer 15 is provided along an inner circumference of the touch sensing unit 20 to ground static electricity introduced into the touch key 10.
An electromagnetic interference (EMI) paint 14 is coated onto the entire surface of the touch sensing unit 20. The EMI paint 14 includes a conductive material to let a current flow. Static electricity introduced into the touch key 10 is absorbed by the ground layer 15 and then is discharged through the EMI paint 14 and the connector unit 30.
The lower layer 13 includes light emitting diodes (LEDs, not shown) for illuminating the touch key 10 in positions corresponding to the position of the touch sensing unit 20.
However, since both the touch sensing unit 20 and the LEDs are formed at a side of the ground layer 15, static electricity introduced into the touch key 10 may bounce to the LEDs and the touch sensing unit 20. Due to the bounce of static electricity absorbed by the ground layer 15, static electricity introduced into the touch sensing unit 20 or the LEDs may damage circuits formed in the touch key 10. Therefore, there is a need for an electrostatic discharge apparatus where static electricity is not introduced into the touch sensing unit 20 or the LEDs.
Moreover, static electricity introduced into the ground layer 15 is discharged through the connector unit 30 after passing through all internal circuits of the touch key 10 resulting in repetitive application of static electricity to the internal circuits of the touch key 10 and the connector unit 30. For this reason, touch key circuits included in the connector unit 30 may be damaged. Therefore, there also is a need for an electrostatic discharge apparatus capable of discharging static electricity that is repetitively applied to the connector unit 30. To discharge generated static electricity, the entire surface of the touch key 10 is coated with the EMI paint 14; however, parts included in the touch sensing unit 20 are damaged by the coated EMI paint 14. Therefore, there is a need for an electrostatic discharge apparatus capable of preventing the EMI paint 14 from being coated onto the entire surface of the touch sensing unit 20 and discharging static electricity without passing it through an internal circuit of the touch sensing unit 20.